How do I see my swimming sessions in the Garmin calendar as an activity vs. as a note - I have added one of the triathlon training plans and as expected the run / bike entries have pulled through - but the swim session appear only as 'notes' in the little speech bubble type icons in the calendar itself. I assume there is a setting buried somewhere which means I can see these as calendar activities and therefore sync. them to my device?
At a guess, the triathlon training plans could have been designed (by their respective creators as credited, not Garmin) before swim workouts were available as a type of structured workout in Garmin Connect, and so the creators worked with what they had access to at the time, and left it at that.
That is exactly it, the tri training plans were created before swim workouts were supported. If you want to add them to your training plan as workouts you will need to create those workouts yourself using the note as a guide and put them on your calendar. It will ask if you want to add them to the training plan.